Water-cooled stator bars for electrical generators are comprised of a plurality of small rectangular solid and hollow copper strands which are brazed to one another and brazed to an end fitting. The end fitting serves as both an electrical and a hydraulic connection for the stator bar. The end fitting typically includes an enclosed chamber for ingress or egress of stator bar cooling liquid, typically deionized water. Another opening of the end fitting receives the ends of the strands of the stator bar, the fitting and peripherally outermost copper strands of the stator bar being brazed to one another. Over time, leaks have variously developed about the connection between the stator bar ends and the stator bar fitting as well as between adjacent strands. It is believed, based on leak analysis results, that the leak mechanism is due to a two-part corrosion process which initiates in the braze alloy at the interior surface of the braze joint. Stagnant water in contact with the braze alloy and the copper strands, is believed to cause corrosion and consequent leakage.
Field repair of leaks through the stator bar end connections has only been moderately successful. Typically, a leak site is identified by external visual examination methods where the strands enter the end fitting. External visual leak detection, however, can only indirectly identify the leak site because the external evidence of the leak may be located a considerable distance from the actual leak path. This is particularly true if the leak is occurring between the strands of the stator bar. Once a leak is identified in this manner, a vacuum is drawn inside the fitting and stator bar. An anaerobic cement is then applied externally around the suspected leak sites, the vacuum suction drawing the cement inwardly into the leak path. However, it has been found that this repair method is not 100% effective in repairing the leak and is therefore considered only a temporary repair. Frequently, the inability to repair leakage through the stator bar end connections forces generator owners to replace the leaking bars or the entire stator winding to eliminate the leaks. This replacement, of course, is expensive and requires significant generator downtime.